Motorized vehicles may include a shift-by-wire system electrically coupling an automatic transmission of the vehicle to an instrument panel within a cabin of the vehicle. A user may interact with the instrument panel in order to select a gear mode of the transmission. For example, the instrument panel may include a selector dial, and the user may rotate the selector dial to change the gear mode of the transmission to drive, park, neutral, etc. A powertrain control module (PCM) is electrically coupled between the selector dial and the transmission, and the PCM sends a signal to the transmission to change the gear mode in response to a rotation of the selector dial. A servo assembly is often coupled with a park rod and actuated by a hydraulic system of the transmission to engage the park rod with a park pawl when the user changes the gear mode to park. The park pawl engages a park gear of the transmission and locks a rotation of the park gear, thereby preventing the vehicle from moving. The park gear may be unlocked by disengaging the park rod with the park pawl.
One example approach is shown by Landino et al. in U.S. Patent 2014/0123799. Therein, a system for locking a park device of a transmission in an out-of-park mode of operation includes a valve body that defines a bore, a solenoid connected to the valve body, a lock feature disposed in the valve body and interconnected with the solenoid, and a servo piston disposed within the bore of the valve body. The servo piston is coupled with a rod, and hydraulic fluid assists with a movement of the servo piston in order to adjust a mode of the transmission between a park mode and the out-of-park mode. A lock ball is included within the valve body and is used to lock the servo piston into a position corresponding with the out-of-park mode.
However, the inventors herein have recognized potential issues with such systems. As one example, the lock ball may become lodged into its locked position and cause the transmission to be unable to disengage from the out-of-park mode. Additionally, hybrid electric vehicles may not include a hydraulic system capable of generating enough hydraulic pressure to adjust the position of the servo piston and/or the lock ball.
In one example, at least some of the issues described above may be addressed by a park lock system, comprising: a park rod adapted to engage with a park lever of an automatic transmission; a slideable element, including: a first end directly coupled to the park rod; and a slot formed at a second end; a pivotable pawl shaped to couple with the slot; a cam engaged with the pivotable pawl and coupled to a shaft; and a solenoid electromechanically coupled to the shaft. In one example, a motor (e.g., an electric motor) may adjust a position of the slideable element (and therefore, the park rod) so that the transmission is in an out-of-park mode. The shaft may be biased by a biasing member toward the pivotable pawl, and the solenoid may be energized to further urge the cam against the pivotable pawl, thereby pivoting the pivotable pawl to couple with the slot. Coupling the pivotable pawl with the slot locks the transmission into the out-of-park mode. The transmission may be released from the out-of-park mode by de-energizing the solenoid.
In this way, the transmission may return from the out-of-park mode to the park mode when the solenoid is de-energized (e.g., when the vehicle is not in operation). Additionally, due to the biasing of the shaft toward the pivotable pawl by the biasing member, a solenoid with a smaller size may be used to lock transmission into the out-of-park mode. The motor and solenoid may be powered by an electrical system of the vehicle such that the park lock system operates without a hydraulic system, thereby reducing an overall packaging size of the transmission.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.